If two molecules exhibit ONLY London Dispersion force, which one will have more London Dispersion, and therefore a higher melting point?

The more electrons a molecule has the higher the boiling point.

Explanation:

Although the london forces are the same, the more electrons a molecule has then more energy is required to separate them hence resulting in a higher boiling point.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.